Liquid ejecting head, liquid ejecting apparatus, and actuator

ABSTRACT

A liquid ejecting head includes a piezoelectric element and a vibrating plate configured to vibrate in response to actuation of the piezoelectric element, the vibrating plate including a first layer that contains SiO 2  and a second layer that contains ZrO 2  and that is stacked on the first layer. The second layer contains a first impurity element different from Zr, and the concentration of the first impurity element at an interface in contact with the first layer in the second layer is higher than the concentration of the first impurity element in an internal region that is included in the second layer and that is contiguous from the interface to the surface of the second layer.

The present application is based on, and claims priority from JPApplication Serial Number 2020-163341, filed Sep. 29, 2020, thedisclosure of which is hereby incorporated by reference herein in itsentirety.

BACKGROUND 1. Technical Field

The present disclosure relates to a liquid ejecting head, a liquidejecting apparatus, and an actuator.

2. Related Art

A liquid ejecting head provided with a vibrating plate including aninsulating film composed of ZrO₂ and an elastic film composed of SiO₂and provided with a piezoelectric element that displaces the vibratingplate is known (for example, JP-A-2008-78407).

The insulating film may have residual stress such as tensile stress.Consequently, when an external force is applied to the vibrating platein response to actuation of the piezoelectric element, the vibratingplate may crack.

SUMMARY

According to a first aspect of the present disclosure, a liquid ejectinghead is provided. The liquid ejecting head includes a piezoelectricelement and a vibrating plate configured to vibrate in response toactuation of the piezoelectric element, the vibrating plate including afirst layer that contains SiO₂ and a second layer that contains ZrO₂ andthat is stacked on the first layer. The second layer contains a firstimpurity element different from Zr and the concentration of the firstimpurity element at an interface in contact with the first layer in thesecond layer may be higher than the concentration of the first impurityelement in an internal region that is included in the second layer andthat is contiguous from the interface to the surface of the secondlayer.

According to a second aspect of the present disclosure, a liquidejecting apparatus is provided. The liquid ejecting apparatus includesthe liquid ejecting head according to the first aspect and a controlportion that controls an ejection operation of the liquid ejecting head.

According to a third aspect of the present disclosure, an actuator isprovided. The actuator includes a piezoelectric element and a vibratingplate configured to vibrate in response to actuation of thepiezoelectric element, the vibrating plate including a first layer thatcontains SiO₂ and a second layer that contains ZrO₂ and that is stackedon the first layer. The second layer contains a first impurity elementdifferent from Zr and the concentration of the first impurity element atan interface in contact with the first layer in the second layer may behigher than the concentration of the first impurity element in aninternal region that is included in the second layer and that iscontiguous from the interface to the surface of the second layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory diagram illustrating a liquid ejectingapparatus according to the present embodiment.

FIG. 2 is a plan view of a liquid ejecting head.

FIG. 3 is a sectional view cut along line III-III in FIG. 2 .

FIG. 4 is an enlarged explanatory diagram illustrating a vibratingplate.

FIG. 5 is an explanatory diagram illustrating examples of concentrationdistributions of elements contained in an elastic film and an insulatorfilm.

FIG. 6 is an explanatory diagram illustrating the film thickness of aninsulator film versus the distribution of the residual stress.

FIG. 7 is an explanatory diagram illustrating examples of concentrationsof impurity elements in a vibrating plate containing Hf as a secondimpurity element.

DESCRIPTION OF EXEMPLARY EMBODIMENTS A. First Embodiment

FIG. 1 is an explanatory diagram illustrating a liquid ejectingapparatus 100 equipped with a liquid ejecting head 1 according to thepresent embodiment. The liquid ejecting apparatus 100 is a printingapparatus of an ink jet system that ejects a liquid ink. The liquidejecting apparatus 100 includes a liquid container 2 configured to storethe ink, and an image is formed on a medium PM by using the ink in theliquid container 2. FIG. 1 schematically illustrates the X-direction,the Y-direction, and the Z-direction orthogonal to each other. Eachdirection illustrated in FIG. 1 is common to FIG. 1 and subsequentdrawings.

The liquid ejecting apparatus 100 includes the liquid ejecting head 1, amovement mechanism 24, a transport mechanism 8, and a control unit 121.The liquid ejecting head 1 is an ink jet-type recoding head configuredto eject an ink supplied from the liquid container 2. The movementmechanism 24 includes a ring-like belt 24 b and a carriage 24 cconfigured to hold the liquid ejecting head 1. The carriage 24 c isfixed to the belt 24 b. The movement mechanism 24 reciprocates theliquid ejecting head 1 together with the carriage 24 c in a movementdirection by rotating the belt 24 b in both forward and reversedirections. The transport mechanism 8 transports the medium PM in adirection intersecting the movement direction of the liquid ejectinghead 1.

The control unit 121 functions as a control portion that forms an imageon the medium PM by operating the transport mechanism 8, the movementmechanism 24, and the liquid ejecting head 1 in accordance with eachother. More specifically, the control unit 121 forms an image on themedium PM by repeatedly controlling ink ejection from the liquidejecting head 1 and reciprocating the liquid ejecting head 1 based oncontrol of the operation of the movement mechanism 24, while the mediumPM is transported by controlling the operation of the transportmechanism 8.

FIG. 2 is a plan view of the liquid ejecting head 1. Regarding theliquid ejecting head 1 in FIG. 2 , the surface facing the medium PM isprovided with a nozzle plate 20. A plurality of nozzles 21 are arrangedin one direction in the nozzle plate 20.

FIG. 3 is a sectional view cut along line III-III in FIG. 2 . The liquidejecting head 1 includes a flow-passage-forming substrate 10, acommunication plate 15, the nozzle plate 20, a compliance substrate 49,a vibrating plate 50, an actuator 300, a protective substrate 30, and acase member 40. Regarding the example in FIG. 3 , the ink ejectiondirection of the nozzle 21 is in accord with the Z-direction. For thesake of facilitating understanding of the technology, in the followingexplanations, the ink ejection direction with respect to a referenceposition is also referred to as “down”, and the direction opposite tothe ink ejection direction with respect to the reference position isalso referred to as “up”.

The flow-passage-forming substrate 10 is a flat-plate-like member. Theflow-passage-forming substrate 10 includes a pressure chamber 12. Thecommunication plate 15 is arranged on the lower-surface side of theflow-passage-forming substrate 10. The communication plate 15 is formedby stacking a first communication plate 151 and a second communicationplate 152, which have ink flow passages. The ink flow passages of thecommunication plate 15 include a first communication portion 16, asecond communication portion 17, a third communication portion 18, afirst flow passage 201, a second flow passage 202, and a supply passage203. The first flow passage 201, the second flow passage 202, the supplypassage 203, and the pressure chamber 12 are in communication with eachother and constitute the ink flow passages. The number of the first flowpassages 201, the second flow passages 202, the supply passages 203, andthe pressure chambers 12 formed and arranged in the arrangementdirection of the nozzles 21 corresponds to the number of the nozzles 21.The first flow passage 201, the second flow passage 202, the supplypassage 203, and the pressure chamber 12 collectively constitute anindividual flow passage 200. One each of the first communication portion16, the second communication portion 17, and the third communicationportion 18 is formed and functions as an ink flow passage common to aplurality of individual flow passages 200.

The nozzle plate 20 is arranged on the lower-surface side of thecommunication plate 15. The nozzle plate 20 blocks part of the openingon the lower-surface side of the communication plate 15 and functions asthe inner wall of the first flow passage 201, the second flow passage202, and the third communication portion 18, which serve as the ink flowpassages. The nozzle 21 is formed at the position that blocks the firstflow passage 201 of the nozzle plate 20.

The compliance substrate 49 is arranged on the lower-surface side of thecommunication plate 15 so as to surround the nozzle plate 20. Thecompliance substrate 49 blocks part of the opening on the lower-surfaceside of the communication plate 15 and functions as part of the innerwall of the first communication portion 16 serving as the ink flowpassage. The compliance substrate 49 includes a sealing film 491 and afixed substrate 492. The fixed substrate 492 is arranged on thelower-surface side of the sealing film 491. The fixed substrate 492includes a compliance portion 494 in a region sealing the firstcommunication portion 16. The compliance portion 494 is an opening whichis formed in the fixed substrate 492 and at which the sealing film 491is exposed. The compliance portion 494 is arranged in a region sealingthe first communication portion 16 of the communication plate 15.Consequently, the sealing film 491 can be elastically deformed inward ofthe opening of the fixed substrate 492 so as to smooth fluctuations ofthe pressure in the first communication portion 16.

The protective substrate 30 is a substrate for housing the actuator 300.A recessed actuator-holding portion 31 is included in the protectivesubstrate 30. A space for housing a plurality of deformable actuators300 is delimited by the actuator-holding portion 31.

The case member 40 is a member for covering the upper surfaces of theflow-passage-forming substrate 10, the communication plate 15, and theprotective substrate 30. The case member 40 has a coupling hole 45 andink flow passages. The coupling hole 45 is a through hole thatvertically passes through the case member 40. A flexible cable 120provided with a driving circuit 126 is arranged in the coupling hole 45.The driving circuit 126 is a semiconductor element for supplying adriving signal for actuating a piezoelectric element 32. The flexiblecable 120 is electrically coupled to a lead electrode 90 in the couplinghole 45.

The ink flow passages of the case member 40 include a first liquidchamber portion 41, a second liquid chamber portion 42, an inlet 43, andan outlet 44. The inlet 43 and the outlet 44 are coupled to an inkstorage chamber (not illustrated in the drawing). The first liquidchamber portion 41 is in communication with the first communicationportion 16 of the communication plate 15, and the second liquid chamberportion 42 is in communication with the second communication portion 17of the communication plate 15.

In FIG. 3 , the flow direction of the ink is schematically illustratedby using arrows. The ink supplied from an ink storage portion isintroduced into the first liquid chamber portion 41 in the case member40 through the inlet 43. The flow of the ink supplied to the firstliquid chamber portion 41 that flows to the first communication portion16 of the communication plate 15 and branches into each of the pluralityof individual flow passages 200. Each of the branched ink flows throughthe supply passage 203, the pressure chamber 12, the second flow passage202, and the first flow passage 201 in this order and merges whenreaching the third communication portion 18. The ink supplied to thethird communication portion 18 flows through the second communicationportion 17 to the second liquid chamber portion 42 and is dischargedthrough the outlet 44 to the ink storage portion. The ink discharged tothe ink storage portion is circulated and reintroduced through the inlet43.

The actuator 300 is arranged at the upper surface of theflow-passage-forming substrate 10. The actuator 300 converts an inputelectrical signal to physical movement and transfers this movement tothe ink in the pressure chamber 12. The actuator 300 includes thepiezoelectric element 32 and the vibrating plate 50. The piezoelectricelement 32 includes a first electrode 60, a piezoelectric layer 70, anda second electrode 80.

The piezoelectric layer 70 is arranged between the first electrode 60and the second electrode 80. The piezoelectric layer 70 is a layercomposed of, for example, lead zirconate titanate (PZT) and deforms inresponse to application of a voltage. The piezoelectric layer 70 is notlimited to PZT, and other ferroelectric piezoelectric materials, relaxorferroelectric materials in which a metal such as niobium, nickel,magnesium, bismuth, or yttrium is added to the ferroelectricpiezoelectric material, and the like may be used.

The first electrode 60 disposed below the piezoelectric layer 70 is acommon electrode of the piezoelectric element 32, and the secondelectrode 80 disposed above the piezoelectric layer 70 is an individualelectrode of the piezoelectric element 32. The lead electrode 90 iscoupled to the second electrode 80. A driving signal output from thedriving circuit 126 is supplied to the second electrode 80 via theflexible cable 120 and the lead electrode 90. A voltage is applied tothe piezoelectric layer 70 by the first electrode 60 and the secondelectrode 80 to deform the piezoelectric layer 70. In this regard, thefirst electrode 60 disposed below the piezoelectric layer 70 may be setto be an individual electrode, and the second electrode 80 disposedabove the piezoelectric layer 70 may be set to be a common electrode.

The vibrating plate 50 is arranged at the upper surface of theflow-passage-forming substrate 10 while being in contact with theactuator 300. The vibrating plate 50 is vibrated in response toactuation of the piezoelectric element 32, that is, deformation of thepiezoelectric layer 70, so as to apply pressure to the ink in thepressure chamber 12. The ink is ejected from the nozzle 21 by thepressure fluctuations of the ink in the pressure chamber 12 beingtransferred to the ink in the second flow passage 202 and the first flowpassage 201.

The vibrating plate 50 includes the insulator film 51 and the elasticfilm 52. The elastic film 52 is a layer containing silicon dioxide(SiO₂). The elastic film 52 is also referred to as a “first layer 52”.The thickness of the elastic film 52 may be set to be 0.1 μm or more and0.5 μm or less. The elastic film 52 is arranged at theflow-passage-forming substrate 10 and blocks the opening on theupper-surface side of the flow-passage-forming substrate 10. Theinsulator film 51 containing zirconium oxide (ZrO₂) is stacked on theelastic film 52. The insulator film 51 is also referred to as a “secondlayer 51”. The thickness of the insulator film 51 may be set to be 0.1μm or more and 1.2 μm or less. In the present embodiment, the insulatorfilm 51 contains ZrO₂ having a columnar crystal structure. In thisregard, the insulator film 51 contains monoclinic ZrO₂. In the presentembodiment, the elastic film 52 and the insulator film 51 contain, forexample, a total amount of less than 10% by mass of impurity elements.The form of the impurity element contained in the insulator film 52 andthe insulator film 51 may be in an atomic form, in an elemental form, orin a molecule such as an oxide.

Regarding the method for forming the vibrating plate 50, silicon waferfor forming the flow-passage-forming substrate 10 is subjected tothermal oxidation in a diffusion furnace at substantially 1,100 degreesCelsius so as to form a silicon dioxide film serving as the elastic film52 on the surface. A zirconium (Zr) layer is formed on the resultingelastic film 52 by using, for example, a sputtering method, andperforming thermal oxidation in a diffusion furnace at 500 degreesCelsius or higher and 1,200 degrees Celsius or lower so as to form theinsulator film 51 containing zirconium oxide. Examples of the method foran impurity element to be contained in the insulator film 51 include amethod in which, when the insulator film 51 is formed by using thesputtering method, the insulator film 51 is formed through sputtering byusing a target already containing the impurity element. Theconcentration of the impurity element contained in the insulator film 51can be controlled by increasing or decreasing the concentration of theimpurity element in the sputtering target. Specifically, theconcentration of the impurity element can be increased by increasing theconcentration of the impurity element in the sputtering target.

FIG. 4 is an enlarged explanatory diagram illustrating region IV in FIG.3 . For the sake of facilitating understanding of the technology,members other than the vibrating plate 50 are omitted from FIG. 4 . InFIG. 4 , the interface IF of the insulator film 51, the surface SR1 ofthe insulator film 51, the internal region IA1 of the insulator film 51,the surface SR2 of the elastic film 52, and the internal region IA2 ofthe elastic film 52 are schematically illustrated. The interface IFdenotes a region of the insulator film 51 in contact with the elasticfilm 52. In general, the interface of a multilayer body in which aplurality of layers are stacked may become a cracking start point andmay become the reason for causing a deterioration in the strength of themultilayer body. The surface SR1 of the insulator film 51 is a surfaceincluded in a region opposite to the elastic film 52 with the interfaceregion FA interposed therebetween and is a surface opposite to theinterface IF of the insulator film 51. As illustrated in FIG. 3 , thesurface SR1 of the insulator film 51 is a surface in contact with thepiezoelectric element 32. The internal region IA1 of the insulator film51 is a region contiguous from the interface IF to the surface SR1 ofthe insulator film 51. The surface SR2 of the elastic film 52 is asurface opposite to the surface of the elastic film 52 in contact withthe insulator film 51. The internal region IA2 of the elastic film 52 isa region from the surface SR2 of the elastic film 52 to the surface incontact with the insulator film 51. The interface IF is not limited tothe region of the insulator film 51 in contact with the elastic film 52and may include part of the internal region IA1 contiguous from theregion of the insulator film 51 in contact with the elastic film 52.

FIG. 5 is an explanatory diagram illustrating examples of concentrationdistributions of elements contained in the elastic film 52 and theinsulator film 51. FIG. 5 illustrates the measurement results of thefilm thickness of the vibrating plate 50 versus the secondary ionintensity of each element and each molecule by using secondary ion massspectrometry (SIMS), that is, the film thickness of the vibrating plate50 versus the concentration distribution of each element and eachmolecule. The vertical axis of FIG. 5 represents the secondary ionintensity, and the horizontal axis represents the depth from the surfaceSR1 of the insulator film 51, that is, the film thickness of thevibrating plate 50. In FIG. 5 , the position of the surface SR1 and theposition of the interface IF of the elastic film 52 and the insulatorfilm 51 are illustrated on the horizontal axis. For the sake offacilitating understanding of the technology, the position of theinterface IF, the position of the surface SR2 of the elastic film 52serving as a SiO₂ layer, and the position of the surface SR1 of theinsulator film 51 serving as a ZrO₂ layer are schematically illustratedbelow the horizontal axis of FIG. 5 .

Regarding the method for measuring the secondary ion intensity, a sampleof the vibrating plate 50 cut to a size of 2 cm×2 cm is prepared.Regarding the method for forming the vibrating plate 50, as describedabove, a silicon dioxide film serving as the elastic film 52 is formedon the silicon wafer surface, a zirconium layer is formed on theresulting elastic film 52, and the insulator film 51 containingzirconium oxide is formed through thermal oxidation. The prepared sampleof the vibrating plate 50 is exposed to a heavy-water atmosphere that isa relatively heavy-water-rich environment at a temperature of 45 degreesCelsius and a humidity of 95% for 24 hours and is thereafter recovered.The recovered sample of the vibrating plate 50 is placed into asecondary ion mass spectrometer and measured. Examples of themeasurement target element include hydrogen, deuterium, oxygen, silicon,zirconium, titanium, aluminum, iron, and chromium.

In the present embodiment, the impurity elements contained in theelastic film 52 and the insulator film 51 include a first impurityelement and a second impurity element. The impurity element of theelastic film 52 does not include Si, and the impurity element of theinsulator film 51 does not include Zr. The first impurity element andthe second impurity element differ from each other due to a differencein the trend of the concentration distribution in the insulator film 51.

The first impurity element denotes an impurity element, theconcentration of which is higher at the interface IF than in theinternal region IA1 of the insulator film 51. In the example illustratedin FIG. 5 , chromium (Cr) and iron (Fe) correspond to the first impurityelement. For example, Cr is present as chromium(II) oxide represented bya composition formula CrO, and Fe is present as iron(II) oxiderepresented by a composition formula FeO. Cr may be present aschromium(III) oxide represented by a composition formula Cr₂O₃,chromium(IV) oxide represented by a composition formula CrO₂, orchromium(VI) oxide represented by a composition formula CrO₃. It isconjectured that, when the insulator film 51 is formed by subjecting theZr layer arranged on the elastic film 52 to thermal oxidation, the causeof the concentration of the first impurity element being higher at theinterface IF than in the internal region IA1 is due to the firstimpurity element contained in the insulator film 51 moving toward theinterface IF in accordance with the Zr layer being successively oxidizedfrom the surface SR1 toward the interface IF. The first impurity elementmay be a metal element. In this regard, the internal region IA1 of theinsulator film 51 is not limited to containing the first impurityelement.

In the present embodiment, the first impurity elements of the insulatorfilm 51 further include Si in addition to Cr and Fe. As illustrated inFIG. 5 , regarding the Si concentration distribution, the Siconcentration is higher at the interface IF than in the internal regionIA1. As indicated by a region PA in FIG. 5 , the Si concentrationdistribution has a planar region (equivalent to a plateau region) inwhich the concentration is constant in the internal region IA1 of theinsulator film 51. In this regard, the Si concentration distribution inthe internal region IA1 gradually increases with increasing proximity tothe interface IF.

In the present embodiment, the first impurity element is not containedin the elastic film 52. However, the first impurity element may becontained in the elastic film 52. In such an instance, the concentrationof the first impurity element in the elastic film 52 may be lower thanthe concentration of the first impurity element at the interface IF andmay be lower than the concentration of the first impurity element in theinternal region IA1 of the insulator film 51.

The second impurity element denotes an element, the concentration ofwhich tends to be substantially constant in the insulator film 51. Inthe example illustrated in FIG. 5 , Ti corresponds to the secondimpurity element. For example, Ti is present as titanium monoxiderepresented by a composition formula TiO. Ti may be present as titaniumdioxide represented by a composition formula TiO₂ or titanium(III) oxiderepresented by a composition formula Ti₂O₃. It is conjectured that thecause of the concentration of the second impurity element being constantis due to the thermal oxidation of the second impurity element that hasdiffused into the Zr layer formed on the elastic film 52 throughsputtering proceeding with Zr. The second impurity element may be ametal element and may be more favorably a metal element having a largerparticle diameter than Zr.

In the insulator film 51, the difference DF1 between the concentrationof the second impurity element at the interface IF and the concentrationof the second impurity element in the internal region IA1 is smallerthan the difference DF2 between the concentration of Cr serving as thefirst impurity element at the interface IF and the concentration of Crin the internal region IA1. In other words, the second impurity elementis an impurity element, the concentration of which is not higher at theinterface IF than in the internal region IA1. The concentration of thefirst impurity element at the interface IF may be equal to theconcentration of the first impurity element in the internal region IA1.

FIG. 6 is an explanatory diagram illustrating the film thickness of theinsulator film 51 versus the distribution of the residual stress. FIG. 6illustrates the measurement results of the residual stress of foursamples of the insulator film 51 that differ from each other in theconcentration of the first impurity element. The horizontal axis of FIG.6 represents the film thickness from the interface IF to the surface SR1of the insulator film 51, and the vertical axis of FIG. 6 represents theresidual stress of the insulator film 51. The residual stress wasmeasured by using a thin film stress measuring apparatus. The residualstress was obtained by acquiring the curvature of a sample andperforming conversion to stress. The residual stress of each sample ofthe insulator film 51 is the result of measurement performed after theresidual film thickness TH4 at the surface SR1 of the insulator film 51was set to each of the residual film thicknesses TH1, TH2, and TH3 asthe internal region IA1 and up to the residual thickness TH0 at theinterface IF through ion milling by using argon ions. The concentrationsof the first impurity element in Samples S1 to S3 are less than 10% bymass and differ from each other. Specifically, the concentration of thefirst impurity element in Sample S1 is lowest, the concentration of thefirst impurity element in Sample S3 is highest, and the concentration ofthe first impurity element in Sample S2 is higher than the concentrationin Sample S1 and lower than the concentration in Sample S3. As thecomparative example, FIG. 6 illustrates the result of Sample SR notcontaining the first impurity element.

As illustrated by Sample SR in FIG. 6 , when the insulator film 51 doesnot contain the first impurity element, the residual stress of each ofthe interface IF to the surface SR1 of the insulator film 51 is tensilestress. Regarding Samples S1 to S3 at the residual film thickness TH0,as illustrated in FIG. 6 , the interfaces IF of the insulator films 51have compressive stress. The compressive stress at the interface IFincreases as the concentration of the first impurity element increasesand is maximum in Sample S3 in which the concentration of the firstimpurity element is highest. Regarding Samples S1 to S3, the residualstress at locations other than the interface IF, that is, at each of theresidual film thickness TH4 at the surface SR1 of the insulator film 51and the residual film thicknesses TH1, TH2, and TH3 in the internalregion IA1 is tensile stress. In Samples S1 to S3, the tensile stress atthe surface SR1 is greater than the tensile stress in the internalregion IA1.

As described above, according to the liquid ejecting head 1 of thepresent embodiment, the vibrating plate 50 includes the elastic film 52containing SiO₂ and the insulator film 51 containing ZrO₂. The insulatorfilm 51 contains the first impurity element, the concentration of thefirst impurity element at the interface IF of the insulator film 51 ishigher than the concentration of the first impurity element in theinternal region IA1. The strength of the vibrating plate 50 can beimproved by providing residual compressive stress in the interfaceregion FA, which tends to be a cracking start point.

According to the liquid ejecting head 1 of the present embodiment, thefirst impurity element contains a metal element. Therefore, theconcentration of the first impurity element at the interface IF can befurther increased, and the strength of the vibrating plate 50 can befurther improved.

According to the liquid ejecting head 1 of the present embodiment, thefirst impurity element contains Fe. Therefore, the concentration of thefirst impurity element at the interface IF can be further increased, andthe strength of the vibrating plate 50 can be further improved.

According to the liquid ejecting head 1 of the present embodiment, thefirst impurity element contains Cr. Therefore, the concentration of thefirst impurity element at the interface IF can be further increased, andthe strength of the vibrating plate 50 can be further improved.

According to the liquid ejecting head 1 of the present embodiment, thefirst impurity element contains Si. Therefore, the adhesiveness betweenthe insulator film 51 and the elastic film 52 can be improved, and thestrength of the vibrating plate 50 can be improved.

According to the liquid ejecting head 1 of the present embodiment, theinternal region IA1 of the insulator film 51 contains the first impurityelement. Therefore, the vibrating plate 50 in which the internal regionIA1 of the insulator film 51 contains the first impurity element can beobtained.

According to the liquid ejecting head 1 of the present embodiment, theinternal region IA1 contains Si serving as the first impurity element.The Si concentration distribution in the internal region IA1 of theinsulator film 51 has a planar region in which the concentration isconstant. Therefore, the vibrating plate 50 in which the internal regionIA1 has a planar region of the Si concentration can be obtained.

According to the liquid ejecting head 1 of the present embodiment, theinsulator film 51 further contains the second impurity element, theconcentration of which in the insulator film 51 is substantiallyconstant. Therefore, the vibrating plate 50 containing the secondimpurity element, the concentration of which in the internal region IA1of the insulator film 51 is substantially constant, can be obtained.

According to the liquid ejecting head 1 of the present embodiment, thesecond impurity element contains a metal element. Therefore, thevibrating plate 50 containing a metal element as the second impurityelement, the concentration of which in the internal region IA1 of theinsulator film 51 is substantially constant, can be obtained.

According to the liquid ejecting head 1 of the present embodiment, thesecond impurity element contains Ti. Therefore, the vibrating plate 50containing Ti, the concentration of which in the internal region IA1 ofthe insulator film 51 is substantially constant, can be obtained.

According to the liquid ejecting head 1 of the present embodiment, theconcentration of the first impurity element in the elastic film 52 islower than the concentration of the first impurity element at theinterface IF and is lower than the concentration of the first impurityelement in the internal region IA1 of the insulator film 51. Theconcentration of the first impurity element in the elastic film 52 canbe reduced, and the productivity of the elastic film 52 can be improved.

According to the liquid ejecting head 1 of the present embodiment, theinsulator film 51 contains ZrO₂ having a columnar crystal structure.Therefore, the adhesiveness between the insulator film 51 and theelastic film 52 can be improved, and peeling and the like of thevibrating plate 50 can be suppressed or prevented from occurring.

According to the liquid ejecting head 1 of the present embodiment,monoclinic ZrO₂ is contained. Therefore, the adhesiveness between theinsulator film 51 and the elastic film 52 can be improved, and peelingand the like of the vibrating plate 50 can be suppressed or preventedfrom occurring.

According to the liquid ejecting head 1 of the present embodiment, theinterface IF of the insulator film 51 has compressive stress. Therefore,the strength of the vibrating plate 50 can be improved by providingresidual compressive stress in the interface region FA, which tends tobe a cracking start point. In addition, the internal region IA1 havingthe tensile stress as the residual stress enables the residual stressbalance of the overall insulator film 51 to be appropriate and enablesthe vibrating plate 50 having higher strength to be obtained.

B. Other Embodiment

(B1) In each of the above-described embodiments, the example in whichthe insulator film 51 contains Ti as the second impurity element isdescribed. On the other hand, the insulator film 51 may contain a secondimpurity element other than Ti. Regarding the second impurity elementcontained in the insulator film 51, Hf may be contained in place of Tior in addition to Ti. Hf may be present as hafnium oxide represented bya composition formula HfO₂. FIG. 7 is an explanatory diagramillustrating examples of concentrations of impurity elements in thevibrating plate 50 containing Hf as the second impurity element. Asillustrated in FIG. 7 , the concentration of Hf in the internal regionIA1 is substantially constant. The difference DF3 between theconcentration of Hf at the interface IF and the concentration of Hf inthe internal region IA1 of the insulator film 51 is smaller than thedifference DF4 between the concentration of Cr serving as the firstimpurity element at the interface IF and the concentration of Cr in theinternal region IA1.

C. Other Aspects

The present disclosure is not limited to the above-described embodimentsand may be realized in various forms within the bounds of not departingfrom the scope of the disclosure. For example, the present disclosuremay be realized in the following aspects. The technical features in theabove-described embodiments corresponding to the technical features inthe aspects described below may be appropriately exchanged or combinedto address some of or all the problems of the present disclosure or toachieve some of or all the effects of the present disclosure. In thisregard, the technical features that are not specified to beindispensable in the specification may be appropriately skipped.

(1) According to an aspect of the present disclosure, a liquid ejectinghead is provided. The liquid ejecting head includes a piezoelectricelement and a vibrating plate configured to vibrate in response toactuation of the piezoelectric element, the vibrating plate including afirst layer that contains SiO₂ and a second layer that contains ZrO₂ andthat is stacked on the first layer. The second layer contains the firstimpurity element different from Zr and the concentration of the firstimpurity element at the interface in contact with the first layer in thesecond layer may be higher than the concentration of the first impurityelement in the internal region that is included in the second layer andthat is contiguous from the interface to the surface of the secondlayer. According to the liquid ejecting head of the present aspect, thestrength of the vibrating plate can be improved, and a cracking problemof the vibrating plate in response to actuation of the piezoelectricelement can be suppressed or prevented.

(2) In the liquid ejecting head according to the above-described aspect,the first impurity element may include a metal element. According to theliquid ejecting head of the present aspect, the strength of thevibrating plate can be further improved.

(3) In the liquid ejecting head according to the above-described aspect,the first impurity element may include Fe. According to the liquidejecting head of the present aspect, the strength of the vibrating platecan be further improved.

(4) In the liquid ejecting head according to the above-described aspect,the first impurity element may include Cr. According to the liquidejecting head of the present aspect, the strength of the vibrating platecan be further improved.

(5) In the liquid ejecting head according to the above-described aspect,the first impurity element may include Si. According to the liquidejecting head of the present aspect, the adhesiveness between the secondlayer and the first layer can be improved.

(6) In the liquid ejecting head according to the above-described aspect,the internal region may contain the first impurity element. According tothe liquid ejecting head of the present aspect, the vibrating plate inwhich the internal region of the second layer contains the firstimpurity element can be obtained.

(7) In the liquid ejecting head according to the above-described aspect,the first impurity element contained in the internal region may includeSi. At least part of the concentration distribution of Si in theinternal region may be a planar region in which the concentration isconstant. According to the liquid ejecting head of the present aspect,the vibrating plate in which the internal region has a planar region ofthe Si concentration can be obtained.

(8) In the liquid ejecting head according to the above-described aspect,the second layer may further contain the second impurity elementdifferent from Zr and from the first impurity element. The differencebetween the concentration of the second impurity element at theinterface and the concentration of the second impurity element in theinternal region may be smaller than the difference between theconcentration of the first impurity element at the interface and theconcentration of the first impurity element in the internal region.According to the liquid ejecting head of the present aspect, thevibrating plate in which the internal region of the second layercontains a substantially constant concentration of the second impurityelement can be obtained.

(9) In the liquid ejecting head according to the above-described aspect,the concentration of the second impurity element at the interface may beequal to the concentration of the second impurity element in theinternal region. According to the liquid ejecting head of the presentaspect, the vibrating plate in which the internal region contains asubstantially constant concentration of the second impurity element canbe obtained.

(10) In the liquid ejecting head according to the above-describedaspect, the second impurity element may include a metal element.According to the liquid ejecting head of the present aspect, thevibrating plate in which the internal region contains a substantiallyconstant concentration of metal element as the second impurity elementcan be obtained.

(11) In the liquid ejecting head according to the above-describedaspect, the second impurity element may include Hf. According to theliquid ejecting head of the present aspect, the vibrating plate in whichthe internal region of the second layer contains Hf can be obtained.

(12) In the liquid ejecting head according to the above-describedaspect, the second impurity element may include Ti. According to theliquid ejecting head of the present aspect, the vibrating plate in whichthe internal region of the second layer contains Ti can be obtained.

(13) In the liquid ejecting head according to the above-describedaspect, the concentration of the first impurity element in the firstlayer may be lower than the concentration of the first impurity elementat the interface and lower than the concentration of the first impurityelement in the internal region. According to the liquid ejecting head ofthe present aspect, the concentration of the first impurity element inthe first layer can be reduced, and the productivity of the first layercan be improved.

(14) In the liquid ejecting head according to the above-describedaspect, the second layer may contain ZrO₂ having a columnar crystalstructure. According to the liquid ejecting head of the present aspect,the adhesiveness between the second layer and the first layer can beimproved, and peeling and the like of the vibrating plate can besuppressed or prevented from occurring.

(15) In the liquid ejecting head according to the above-describedaspect, the second layer may contain monoclinic ZrO₂. According to theliquid ejecting head of the present aspect, the adhesiveness between thesecond layer and the first layer can be improved, and peeling and thelike of the vibrating plate can be suppressed or prevented fromoccurring.

(16) In the liquid ejecting head according to the above-describedaspect, the interface of the second layer may have compressive stressand the internal region of the second layer may have tensile stress.According to the liquid ejecting head of the present aspect, theinterface can be provided with the residual compressive stress, theinternal region can be provided with the tensile stress, and thestrength of the overall vibrating plate can be improved.

(17) According to another aspect of the present disclosure, a liquidejecting apparatus is provided. The liquid ejecting apparatus includesthe liquid ejecting head according to the above-described aspect and acontrol portion that controls an ejection operation of the liquidejecting head. According to the liquid ejecting head of the presentaspect, the liquid ejecting apparatus including the liquid ejecting headin which the strength of the vibrating plate is improved can beobtained.

The present disclosure may be realized in various forms other than theliquid ejecting head. The present disclosure may be realized in theforms of, for example, actuators, liquid ejecting apparatuses, printingapparatuses, methods for controlling liquid ejecting apparatuses,methods for controlling liquid ejecting heads, methods for controllingactuators, liquid ejecting methods, computer programs for realizingthese methods, and non-temporary recording mediums with the recordedcomputer programs.

What is claimed is:
 1. A liquid ejecting head comprising: apiezoelectric element; and a vibrating plate configured to vibrate inresponse to actuation of the piezoelectric element, the vibrating plateincluding a first layer that contains SiO₂ and a second layer thatcontains ZrO₂ and that is stacked on the first layer, wherein the secondlayer contains a first impurity element different from Zr and theconcentration of the first impurity element at an interface in contactwith the first layer in the second layer is higher than theconcentration of the first impurity element in an internal region thatis included in the second layer and that is contiguous from theinterface to the surface of the second layer, wherein the first impurityelement includes a metal element, the metal element including Fe.
 2. Theliquid ejecting head according to claim 1, wherein the first impurityelement includes Cr.
 3. The liquid ejecting head according to claim 1,wherein the first impurity element includes Si.
 4. The liquid ejectinghead according to claim 1, wherein the internal region contains thefirst impurity element.
 5. The liquid ejecting head according to claim4, wherein the first impurity element contained in the internal regionincludes Si and at least part of the concentration distribution of Si inthe internal region is a planar region in which the concentration isconstant.
 6. The liquid ejecting head according to claim 1, wherein thesecond layer further contains a second impurity element different fromZr and from the first impurity element and a difference between theconcentration of the second impurity element at the interface and theconcentration of the second impurity element in the internal region issmaller than a difference between the concentration of the firstimpurity element at the interface and the concentration of the firstimpurity element in the internal region.
 7. The liquid ejecting headaccording to claim 6, wherein the concentration of the second impurityelement at the interface is equal to the concentration of the secondimpurity element in the internal region.
 8. The liquid ejecting headaccording to claim 6, wherein the second impurity element includes ametal element.
 9. The liquid ejecting head according to claim 8, whereinthe second impurity element includes Ti.
 10. The liquid ejecting headaccording to claim 1, wherein the concentration of the first impurityelement in the first layer is lower than the concentration of the firstimpurity element at the interface and lower than the concentration ofthe first impurity element in the internal region.
 11. The liquidejecting head according to claim 1, wherein the second layer containsZrO₂ having a columnar crystal structure.
 12. The liquid ejecting headaccording to claim 1, wherein the second layer contains monoclinic ZrO₂.13. The liquid ejecting head according to claim 1, wherein the interfaceof the second layer has compressive stress and the internal region ofthe second layer has tensile stress.
 14. A liquid ejecting apparatuscomprising: the liquid ejecting head according to claim 1 and a controlportion that controls an ejection operation of the liquid ejecting head.15. A liquid ejecting head comprising: a piezoelectric element; and avibrating plate configured to vibrate in response to actuation of thepiezoelectric element, the vibrating plate including a first layer thatcontains SiO₂ and a second layer that contains ZrO₂ and that is stackedon the first layer, wherein the second layer contains a first impurityelement different from Zr, the concentration of the first impurityelement at an interface in contact with the first layer in the secondlayer is higher than the concentration of the first impurity element inan internal region that is included in the second layer and that iscontiguous from the interface to the surface of the second layer, thesecond layer further contains a second impurity element different fromZr and from the first impurity element, a difference between theconcentration of the second impurity element at the interface and theconcentration of the second impurity element in the internal region issmaller than a difference between the concentration of the firstimpurity element at the interface and the concentration of the firstimpurity element in the internal region, and the second impurity elementincludes Hf.
 16. An actuator comprising: a piezoelectric element; and avibrating plate configured to vibrate in response to actuation of thepiezoelectric element, the vibrating plate including a first layer thatcontains SiO₂ and a second layer that contains ZrO₂ and that is stackedon the first layer, wherein the second layer contains a first impurityelement different from Zr and the concentration of the first impurityelement at an interface in contact with the first layer in the secondlayer is higher than the concentration of the first impurity element inan internal region that is included in the second layer and that iscontiguous from the interface to the surface of the second layer,wherein the first impurity element includes a metal element, the metalelement including Fe.